1. Field of the Invention.
The present invention relates to subsurface well completion equipment and, more particularly, to methods and related apparatus for remotely controlling fluid recovery from multiple laterally drilled wellbores.
2. Description of Related Art.
Hydrocarbon recovery volume from a vertically drilled well can be increased by drilling additional wellbores from that same well. For example, the fluid recovery rate and the well's economic life can be increased by drilling a horizontal or highly deviated interval from a main wellbore radially outward into one or more formations. Still further increases in recovery and well life can be attained by drilling multiple deviated intervals into multiple formations. Once the multilateral wellbores have been drilled and completed there is a need for the recovery of fluids from each wellbore to be individually controlled. Currently, the control of the fluid recovery from these multilateral wellbores has been limited in that once a lateral wellbore has been opened it is not possible to selectively close off and/or reopen the lateral wellbores without the need for the use of additional equipment, such as wireline units, coiled tubing units and workover rigs.
The need for selective fluid recovery is important in that individual producing intervals usually contain hydrocarbons that have different physical and chemical properties and as such may have different unit values. Co-mingling a valuable and desirable crude with one that has, for instance, a high sulfur content would not be commercially expedient, and in some cases is prohibited by governmental regulatory authorities. Also, because different intervals inherently contain differing volumes of hydrocarbons, it is highly probable that one interval will deplete before the others, and will need to be easily and inexpensively closed off from the vertical wellbore before the other intervals.
The use of workover rigs, coiled tubing units and wireline units are relatively inexpensive if used onshore and in typical oilfield locations; however, mobilizing these resources for a remote offshore well can be very expensive in terms of actual dollars spent, and in terms of lost production while the resources are being moved on site. In the case of subsea wells (where no surface platform is present), a drill ship or workover vessel mobilization would be required to merely open/close a downhole wellbore valve.
The following patents disclose the current multilateral drilling and completion techniques. U.S. Pat. No. 4,402,551 details a simple completion method when a lateral wellbore is drilled and completed through a bottom of an existing traditional, vertical wellbore. Control of production fluids from a well completed in this manner is by traditional surface wellhead valving methods, since improved methods of recovery from only one lateral and one interval is disclosed. The importance of this patent is the recognition of the role of orienting and casing the lateral wellbore, and the care taken in sealing the juncture where the vertical borehole interfaces with the lateral wellbore.
U.S. Pat. No. 5,388,648 discloses a method and apparatus for sealing the juncture between one or more horizontal wells using deformable sealing means. This completion method deals primarily with completion techniques prior to insertion of production tubing in the well. While it does address the penetration of multiple intervals at different depths in the well, it does not offer solutions as to how these different intervals may be selectively produced.
U.S. Pat. No. 5,337,808 discloses a technique and apparatus for selective multi-zone vertical and/or horizontal completions. This patent illustrates the need to selectively open and close individual intervals in wells where multiple intervals exist, and discloses devices that isolate these individual zones through the use of workover rigs.
U.S. Pat. No. 5,447,201 discloses a well completion system with selective remote surface control of individual producing zones to solve some of the above described problems. Similarly, U.S. Pat. No. 5,411,085, commonly assigned hereto, discloses a production completion system which can be remotely manipulated by a controlling means extending between downhole components and a panel located at the surface. Each of these patents, while able to solve recovery problems without a workover rig, fails to address the unique problems associated with multilateral wells, and teaches only recovery methods from multiple interval wells. A multilateral well that requires reentry remediation which was completed with either of these techniques has the same problems as before: the production tubing would have to be removed, at great expense, to re-enter the lateral for remediation, and reinserted in the well to resume production.
U.S. Pat. No. 5,474,131 discloses a method for completing multi-lateral wells and maintaining selective re-entry into the lateral wellbores. This method allows for re-entry remediation into deviated laterals, but does not address the need to remotely manipulate downhole completion accessories from the surface without some intervention technique. In this patent, a special shifting tool is required to be inserted in the well on coiled tubing to engage a set of ears to shift a flapper valve to enable selective entry to either a main wellbore or a lateral. To accomplish this, the well production must be halted, a coiled tubing company called to the job site, a surface valving system attached to the wellhead must be removed, a blow out preventer must be attached to the wellhead, a coiled tubing injector head must be attached to the blow out preventer, and the special shifting tool must be attached to the coiled tubing; all before the coiled tubing can be inserted in the well.
There is a need for a system to allow an operator standing at a remote control panel to selectively permit and prohibit flow from multiple lateral well branches drilled from a common central wellbore without having to resort to common intervention techniques. Alternately, there is a need for an operator to selectively open and close a valve to implement re-entry into a lateral branch drilled from the common wellbore. There is a need for redundant power sources to assure operation of these automated downhole devices, should one or more power sources fail. Finally, there is a need for fail safe mechanical recovery tools, should these automated systems become inoperative.